PROJECT SUMMARY/ABSTRACT Up to 75% of antibiotic use in long-term care facilities (LTCFs) is inappropriate or unnecessary. In response and due to increasing evidence of poor outcomes associated with suboptimal antibiotic prescribing in the long- term care setting, the Centers for Medicare and Medicaid Services (CMS) now require that LTCFs implement and maintain antimicrobial stewardship programs as a condition for participation. A major challenge to improving antibiotic utilization in LTCFs is that 40-50% of LTCF antibiotic use is initiated in acute care hospitals prior to LTCF admission. Furthermore, an estimated 70% of antibiotic prescribing on hospital discharge is inappropriate and patients prescribed antibiotics on discharge to a LTCF often lack information regarding the antibiotic indication, duration, and culture results in patients' discharge summaries. At present, there are no interventions specifically targeting antibiotic prescribing on discharge from acute care hospitals to LTCFs. Our long-term goal is to improve antibiotic prescribing in LTCFs and associated patient and resident outcomes. In this application, we will use a mixed methods approach to develop an evidence- based intervention bundle targeting high-value areas to optimize antibiotic prescribing on discharge from hospitals to LTCFs. High-value targets for intervention will be prevalent, modifiable, associated with poor clinical outcomes, and not currently addressed in standard practice. We propose the following specific aims. Specific Aim 1: Identify high-value targets of interventions to optimize antibiotic prescribing on transition from hospitals to LTCFs. We will conduct two multi-center retrospective cohort studies: 1) a hospital-focused study of patients discharged from a network of academic, regional, and community hospitals in Oregon, Washington, and Wisconsin and 2) a LTCF-focused study of residents admitted from hospitals to 23 LTCFs in Oregon, California, Nevada, and Wisconsin. Specific Aim 2: Identify and describe barriers and facilitators of interventions to optimize antibiotic prescribing on transition from hospitals to LTCFs. We will conduct in-depth qualitative interviews among hospital and LTCF healthcare providers, nurses, and administrators. Specific Aim 3: Develop and refine candidate interventions to address high-value targets and gaps identified in Aims 1 and 2. We will use a collaborative process with key hospital and LTCF stakeholders to refine candidate interventions and sequentially test acceptability of the intervention bundle.